This invention relates to a veneer-pressing apparatus for simultaneously pressing a plurality of veneers in multistage.
There has been proposed a pressing apparatus for hot-pressing or cold-pressing a single sheet of veneer or a laminated veneer consisting of a plurality of veneers bonded with each other via an adhesive. For example, Japanese Patent Publication S/41-1753 describes an automatic compression apparatus provided with a plurality of pressing means which are arranged vertically and in multistage.
As shown in FIGS. 14 and 15, this apparatus is generally constituted by a pressing device 200, a loader 206 and an unloader 6. This pressing device 200 comprises a plurality of compression plates 203 which are arranged in multistage or spaced apart vertically from each other by a predetermined interval and interposed between a fixed plate 201 and a movable plate 202 which are vertically spaced apart from each other, and metal belt conveyers 204 (FIG. 15), the upper portion of each metal belt conveyer 204 being disposed to move over the compression plates 203 and adapted to be intermittently moved from a loading side to an unloading side. The loader 206 is movably disposed at the loading side so as to be moved up and down and provided with a plurality of conveyers 205 each arranged to correspond with each of the compression plates 203. The unloader 208 is movably disposed at the unloading side so as to be moved up and down and provided, as in the case of the loader 206, with a plurality of conveyers 205 each arranged to correspond with each of the compression plates 203.
Plates 210 to be treated (hereinafter referred to as untreated plates 210) are successively placed on each conveyer while the loader 206 is vertically moved, and each of the conveyers of the loader 206 is aligned with each of the compression plates 203. Under this condition, the conveyers of the loader 206 and the metal belt conveyers 204 are allowed to move whereby transferring the untreated plates 210 on the conveyers onto the metal belt conveyers 204. Then, the movable plate 202 is moved vertically, thereby rendering the compression plates 203 to approach to each other so as to press each of the untreated plates 210 interposed between the compression plates 203. After keeping this pressing treatment for a predetermined period of time, the movable plate 202 is moved downward thereby allowing the space between the compression plates 203 to expand again. Under this condition, the metal belt conveyers 204 and the conveyers 207 of the unloader 208 are allowed to move whereby transferring the plates 210 thus pressed onto each of the conveyers of the unloader 208. Thereafter, the unloader 208 is moved vertically to successively unload the plates 210 from each of the conveyers 208 toward the unloading conveyers 220.
In this automatic compression apparatus however, the transferring surface (or the upper surface portion) 204a of each of the metal belt conveyers 204 is designed to be moved always in the direction from the loading side to the unloading side (as indicated by the arrow "a"). In this case, the non-transferring surface 204b of the metal belt conveyer 204 which is disposed over the untreated plate 210 is moved in the direction (as indicated by the arrow "b") which is opposite to that of the transferring surface 204a of the metal belt conveyer 204. Accordingly, if an edge portion of the untreated plate 210 is warped or bent upward and if such an untreated plate 210 is to be moved forward through a space between the metal belt conveyers 204, the warped or bent edge portion of the untreated plate 210 may be contacted with the non-transferring surface 204b of the metal belt conveyer 204 that is disposed over the untreated plate 210 and running in the direction opposite to the transferring direction, thus making it difficult to accurately transfer the untreated plate 210 in a predetermined direction and inviting a cause for a fracture of edge portion of the untreated plate 210.
It may be possible to avoid these problems if the interval between the compression plates 203 is set to a sufficient height. However, if the interval between the compression plates 203 is enlarged in this manner, the height of the apparatus will be increased, making the apparatus bulky as a whole, thus inviting another problem.
Additionally, the aforementioned automatic compression apparatus is accompanied with another problem that when a veneer as an untreated plate is hot-pressed, a sap squeezed out of the veneer due to a pressing of the veneer is likely to be adhered onto the bottom portion of the metal belt conveyer disposed over the veneer and running in a direction opposite to the transferring direction. Therefore, if this metal belt conveyer adhered with the sap is allowed to continue to move for transferring the veneer, the veneer may be transferred back to the loading side instead of being transferred to the unloading side, or may be fractured.